U.S. Pat. Nos. 6,228,923 and 6,790,403 incorporated herein by reference, assigned to Stratasys Inc of Eden Prairie, Minn., disclose soluble materials used as support structures in fused deposition modelling (FDM™) methods. A layer by layer method of depositing materials for building a model is described in U.S. Pat. No. 5,121,329 incorporated herein by reference, and numerous other patents assigned to Stratasys, Inc. relate to a fused deposition method or FDM™ methods of model deposition.
Additive process modeling machines form three-dimensional models by building up a modeling medium based upon design data provided from a computer aided design (CAD) system. Three-dimensional models are used for functions including aesthetic judgments, proofing the mathematical CAD model, forming hard tooling, studying interference and space allocation, and testing functionality. A common technique is to deposit solidifiable modeling material in a predetermined pattern, according to design data provided from a CAD system, with the build-up of multiple layers forming the model.
In creating three dimensional objects by additive process techniques, such as by depositing layers of solidifiable material, supporting layers or structures must be used underneath overhanging portions or in cavities of objects under construction, which are not directly supported by the modeling material itself.
A support structure may be built utilizing the same deposition techniques and apparatus by which the modeling material is deposited. The apparatus, under appropriate software control, produces additional geometry acting as a support structure for the overhanging or free-space segments of the object being formed. Support material is deposited either from a separate dispensing head within the modeling apparatus, or by the same dispensing head that deposits modeling material. The support material is chosen so that it adheres to the modeling material. Anchoring the model to such support structures solves the problem of building the model, but creates the additional problem of removing the support structure from the finished model without causing damage to the model.
U.S. Pat. No. 6,228,923 in the name of Lombardi et al., assigned to Stratasys, Inc. discloses the use of poly(2ethyl-2-oxazoline) or PEO, a variety of which is commercially available under the name Aquazol®. PEO is a polar water soluble polymer with rheology and mechanical material properties suitable for use in FDM machines as feedstock.
U.S. Pat. No. 6,790,403 in the name of Priedeman, Jr. et al., assigned to Stratasys, Inc., refers to the use of a polymer consisting of a carboxylic acid base and plasticizer, that is soluble in an alkali solution.
One drawback with Carboxylic acid based polymer is that there is not a great range of temperatures in which it can be used before it degrades and cannot be used. The Carboxylic acid polymer operates at less than 240 degrees C. (<470 degrees F.) in FDM™. We have found that if the Carboxylic melt temperature remains above that for an extended period the material will start to degrade and fail in the machine. Another drawback which we perceive with using Carboxylic acid based polymers is that they are alkali soluble. The alkaline solution required to dissolve the Carboxylic based polymer is noxious, corrosive to skin, an irritant to eyes, and is generally incompatible to an office environment wherein the FDM™ are intended to operate.
A further drawback of the carboxylic acid based polymer is that its glass transition point (Tg) is lower than the envelope temperatures required for deposition of polycarbonate (PC) and polyphenylsulfone (PPSF) materials currently used in FDM machines. If used in this application, the carboxylic acid based polymer would soften and would be unable to act as a support structure.
It is an object of this invention to provide a polymer that is water soluble facilitating dissolving the support and making the process less hazardous. FDM machines using the soluble support media described above have software controls controlling support temp so that it cycles around 230 degree C.
It is an object of this invention to use a water soluble polymer having greater operating temperature headroom to work at that temperature.